Means for providing a choke for in-tube retention of sand in core box or like blow tubes



MEANS FoR PRovImnG'A CHOKE FOR IN-TUBE RETENTION 0F SAND IN com". BOX ORLIKE BLOW TUBES Filed Oct. 15, 1965 Aux-12,1969 R L. OLSON 3,460,607

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I 3 Y A '7 I ORNE S United States Patent 3,460,607 MEANS FOR PROVIDING ACHOKE FOR IN-TUBE RETENTION OF SAND IN CORE BOX OR LIKE BLOW TUBESRichard L. Olson, Hickory Hills, 111., assignor to Dike-O- Seal,Incorporated, Chicago, Ill., a corporation of Illinois Filed Oct. 15,1965, Ser. No. 496,546 Int. Cl. B22c 15/24; Bb 1/50 U.S. Cl. 164-200 6Claims ABSTRACT OF THE DISCLOSURE This invention relates to improvementsin means for blowing sand into core boxes or the like, and moreparticularly concerns a new and improved means for producing a choke forin-tube retention of sand whereby to assure substantially cleanbreakaway of the core from the delivery opening end of the column ofsand in the blow tube.

Heretofore blow tubes or blow passage liners having thereon preformedrestrictions or chokes at the delivery end have been widely used in sandmold blowing and more particularly sand core blowing apparatus. This hasrequired the supplying of a virtually infinite number of lengths of blowtubes because the lengths of the blow holes or passages between theinlet and discharge ends necessarily vary greatly due to variations incore contours and thus in the conforming cavities in the mold or box.

An important object of the present invention is to provide a new andimproved means for providing sand retaining restrictions or chokes forthe purpose described utilizing standardized lengths of blow tubes orblow hole or passage liners.

Another object of the invention is to provide a new and improved meansfor providing a core box or like blow hole with a sand retaining choke.

A further object of the invention is to provide a new and improved sandrestricting choke structure for the blow holes of core boxes and thelike.

Other objects, features and advantages of the present invention will bereadily apparent from the following detailed description of certainpreferred embodiments thereof taken in conjunction with the accompanyingdrawing, in which:

FIGURE 1 is a fragmentary schematic sectional illustration of a sandcore blowing apparatus embodying features of the invention;

FIGURE 2 is a fragmental longitudinal sectional view through a blow tubeof the kind adapted for practicing the invention;

FIGURE 3 is a fragmentary sectional detail view similar to FIGURE 1 butshowing a modification;

FIGURE 4 shows another modification; and

FIGURE 5 shows a further modification.

Sand molding apparatus utilizing the invention, as shown by way ofexample in FIGURE 1, comprises a mold assembly which may be a core boxincluding separable bottom and top sections 11 and 12 provided withorientation pins 12 and defining a core-forming cavity 13. Leading intothe cavity 13 through the upper or cope section 12 of the core box is ablow hole 14 which has its delivery end opening into the cavity and itsupper inlet end, which may be at the upper end of a tubular riser orboss 15, disposed to register with a discharge port 17 in a blow plate18 forming part of means defining a sand magazine from which moldingsand is blown under a substantial pressure head of air with sudden forcethrough the port 17 and the blow hole passage 14 into the cavity 13, airbeing displaced from the cavity through one or more properly locatedscreens 19.

In order to avoid the sand column in the blow tube passage 14 fromdrawing out or falling out of the delivery opening inner end thereofwhen the formed sand core is removed from the cavity 13, a dischargechoke comprising a uniformly tapering constriction 20 terminating at thedelivery opening is desirably provided on the otherwise uniformlycylindrical wall of the blow hole passage 14. This constriction shouldbe as short and as large as practicable consistent with goodperformance. For example, about 10 pitch taper in a choke length ofabout one-half inch has been found highly satisfactory. In producing thechoke 20, a cylindrical hole H may be cored or drilled to the smallestconstriction diameter. Then this hole is reamed out to the desiredcylindrical bore diameter of the blow hole 14, with a nose shape on thereamer having the desired constriction taper by which the choke 20 isformed at the termination of the reaming operation. On the other hand,the choke 20 may be cored directly in the formation of the blow hole 14,or a drill having a pilot end to the shape of the choke constriction maybe utilized.

Inasmuch as the forceful delivery of sand through the blow hole 14 has ahighly erosive effect on the choke constriction 20 where the core boxmember 12 is made from the usual material, of which cast iron, steel,aluminum, and like metals are examples, a liner of erosion resistantmaterial, of which certain polymeric materials are examples and castpolyurethane is a preferred material, is provided. Since even a liner ofpolyurethane will erode after prolonged exposure to repeated sandblowing, the liner is desirable of a replaceable form. To this end, ablow tube 21 having a normal outside diameter substantially the same athe cylindrical diameter of blow hole 14 and of a length at least aslong as the blow hole and with a normally cylindrical inside diameter(FIG. 2) is provided. Such a blow tube is easily manufactured at lowcost from castable polyurethane which in the set condition is of astiffly resiliently yieldable character and is highly abrasionresistant, is possessed of high impact strength, but may be readily cutwith a sharp instrumenL'A wall thickness of about to /e inch has beenfound satisfactory in practice. Assembly of such blow tube 21 into theblow hole 14 is readily effected by inserting it from the entry or outerend toward the cavity 13 and on reaching the choke constriction 20forcing the tube as by pounding it inwardly until its inner end portionconforms to the constriction 20 and completely lines the same, providingthe conforming lining and restriction 20a on the inner surface of theinner or terminal end portion of the tube. To ease driving in of thetube 21 and to facilitate the contracting, cramping, compressing actionof the constriction 20, a lubricant, such as water, oil, silicone,grease or the like, may be applied to the outer surface of the tube orto the constriction. Where the blow tube 21 is longer than the blow hole14, so that after the outer end of the tube has been driven to itslimit, there is a substantial terminal portion of the blow tubeextending beyond the surface contour defining cavity 13 as indicated indashed outine in FIG.

1, such pro ection may be trimmed off with a sharp instrument.

As a drive-in stop and sealing cushion, the outer end portion of theblow tube 21 may be provided with a lateral flange 22 which in theassembly may be received within a counterbore 23 about the other orouter end of the blow hole 14, with a slight projection of the flangeabove the end of the tubular boss 15 for engagement sealingly with theblow plate 18 about the port 17. If preferred, of course, the flange 22may be omitted and the wedging, shouldering coaction of the rigid, fixedconstriction 20 on the core box with the choke restriction 20a of thereplaceable blow tube being relied upon to retain the blow tube againstaxially inward displacement or blowout by the air and sand stream duringcore blowing operation. When desired, the blow tube 21 may be readilyreplaced by driving it out of the blow hole 14. It will be appreciatedthat through this arrangement a few standardized lengths and diametersof the blow tube 21 will suffice to take care of at least a large normalrange of practical core box requirements.

For equipping a blow hole with a lined choke according to the principlesof the present invention, where the blow hole is straight throughcylindrical, as for example in an existing core box, or where it wouldbe impractical, or at least inconvenient, to preform the orifice end ofthe blow hole with a constriction solid in one piece with the box, thetechnique illustrated in FIGURE 3 may be employed. In this instance, thecore box 12 has leading into the cavity chamber 13 the blow hole 14which is cylindrical straight through from its entrance to its dischargeorifice. To provide the tapering constriction 20- an annular insert ofgenerally wedge-shaped construction complementary to the cylindricaldiameter of the blow hole is mounted in the orifice end portion of theblow hole and provides the constriction 20, feathering at its inner endto a knife edge joining the cylindrical wall of the blow hole in asubstantially smooth merger so that the replaceable blow tube 21 can beforced onto the constriction to provide the choke restriction liner 20awith the same efiiciency as where the constriction 20' is a directcontinuation of the wall of the blow hole a in FIGURE 1. Since the blowtube wall is of substantial thickness, it may be relied upon without anencircling boss or other tubular reinforcement, if preferred, as shownin FIG. 3.

Construction of the constriction insert 24 may be in any number ofdifferent ways. For example, it may be made as a preformed metal orrigid plastic annulus of wedge cross section to be driven into theorifice end of the blow hole 14 since its thickest section outer orblunt end aifords substantial impact surface for application of adriving tool. The insert may be of greater length and thus greaterterminal thickness than would normally be necessary to facilitate thedriving in, and the surplus or extra length, as indicated in dashedoutline, trimmed off together with the extra restriction end terminalportion of the blow tube. Alternatively, the insert 24 may be molded insitu from a hard setting, firmly bonding epoxy or other moldable plasticwith or without fillers such as metal pOWder. A material especiallysuitable for the purpose comprises a quick setting polyester compound,commercially available under the trademark Dike-O- Plastic.

Instead of driving an insert into the normal diameter of the blow hole,the arrangement of FIGURE 4 may be used, in which the core box 12 haleading into the coremolding cavity 13 the blow hole 14, in thisinstance extending through the boss 15 and having at its orifice end acounterbore 25 into which is threadedly secured a constriction insert 27which may be formed from any suitable material such as metal or hardplastic to provide the rigid tapered constriction 20 having it inner endmerging with the cylindrical wall of the blow hole. Thereby, similarlyas in the other forms of the invention described, the blow tube 21 isadapted to be driven through the blow hole 14 and the inner end of theblow tube is compressed by the constriction 20 to provide the linerrestriction 20a. If desired, any projecting portions of the insert 27and the blow tube, depicted in dashed outline, may be trimmed off, or ifunobjectionable so far as the surface of the core is concerned, mayremain.

In FIGURE 5 is depicted an arrangement wherein the core box 12 has theblow hole 14 leading thereinto provided by a separately formed metaltube 28 which has an externally reduced diameter end portion 29 receivedin a mounting hole 30 formed in the core box, with a shoulder 31 on themetal tube seating about the hole 30. At the inner end portion of theblow hole 14, the tube 28 is provided with the tapered constriction 20.In this arrangement, the blow tube 21 is driven through the blow hole 14and the tube 28 and through the constriction 20 to provide the chokerestriction 28. The terminal end portion of the tube 21 projectinginwardly beyond the constriction orifice may be trimmed off or, asshown, left in place where a dimple in the surface of the core is notobjectionable.

In all forms of the invention the orifice end of the restriction of theblow tube pinches off the blow tube sand column at/or in the coresurface, whereby that surface is substantially clean when the core isremoved from the core box.

It will be understood that variations and modifications may be effectedwithout departing from the spirit and scope of the novel concepts ofthis invention.

I claim as my invention:

1. In a sand molding apparatus of the character described for use withmeans defining a sand magazine having a port from which sand is blownunder substantial air pressure, a mold member having a molding cavitytherein and a blow hole communicating at one end with said port and atthe opposite end defining an orifice into said cavity,

a tapered rigid constriction defining said blow hole adjacent to andterminating at said orifice, said constriction comprising an insert inthe blow hole having an inner end merging smoothly with the bore of theblow hole, and a replaceable formed liner in said blow hole at least onand conformed to said constriction and defining the actual orificeopening, said liner comprising a highly abrasion resistant material.

2. Apparatus as defined in claim 1 in which the blow 'hole is ofsubstantially uniform diameter throughout its length.

3. Apparatus as defined in claim 1 in which said mold member has acounterbore at the cavity end of said blow hole, and said insert issecured in said counterbore.

4. In a combination according to claim 1, the material of the blow tubebeing cast polyurethane.

5. Apparatus as defined in claim 3 in which the counterbore at thecavity end of said blow hole has threads, and in which said insert hasthreads for engagement with the threads of the counterbore.

6. Apparatus as defined in claim 1 wherein said liner comprises astifily resilient yieldable high impact strength material.

References Cited UNITED STATES PATENTS 2,553,626 5/ 1951 Barlow 164-2002,637,881 5/ 1953 Peterson 164-200 3,104,432 9/ 1963- Peterson 164-200J. SPENCER OVERHOLSER, Primary Examiner ROBERT D. BALDWIN, AssistantExaminer US. Cl. X.R.

